1. (i) Field of the Invention
The present invention relates to an exhaust gas brake more particularly to an improvement in or relating to the construction of a piston rod coupler in an exhaust gas brake system such that there is provided a pneumatic actuator having a piston rod inserted into the opening of a coupler member.
2. (ii) Related Art Statement
It is generally known in the related art that an exhaust brake system is generally designed to be employed mainly in a motor truck or in a bus, and this exhaust brake system is adapted, in addition to the normal wheel brake system, to close a brake valve disposed in the middle of the exhaust gas piping of the vehicle for overcoming an acceleration as arisen in the downhill operation of the vehicle, so that the vehicle's speed may be moderated. The general construction of this exhaust gas brake system is common in use as shown in FIG. 3, for example. Referring more specifically to this construction, there is shown an exhaust gas pipe, which is designated at the reference numeral 1, and through which exhaust gas from an engine is guided to be discharged outwardly in the direction shown by an arrow. A coupler 2 is provided on the way of the exhaust gas pipe 1, in which coupler 2 there is provided a braking valve 3 extending slidably across the passageway of the exhaust gas pipe 1. This coupler 2 is connected by of coupler 4 to pneumatic actuator manner that it extends through an inserting opening 7 of the coupler cover 4 and then projects substantially into the cross opening of the coupler 2, so as to be connected operatively to the braking valve 3. When compressed air is introduced into a pressure chamber 8 of the pneumatic actuator 5, a piston 9 is now forced to move downwardly or in the direction shown by an arrow a in FIG. 3 against the resilient force of a spring 10, so that the braking valve 3 may then be put into a closing position as shown by a chain line in FIG. 3.
More specifically, it is known that the inserting opening 7 of the coupler cover 4 and a passing opening 11 for the piston rod 6 of the pneumatic actuator 5 are given a substantial large clearance, respectively. This clearance is provided specifically for allowing the piston rod 6 to expand from the heat of exhaust gas and for accommodating the resistance to sliding motion of the piston rod 6 to be increased from the deposition of carbon or the like contamination of exhaust gas onto the piston rod 6, accordingly. Unfortunately, however, because of such a substantial large clearance given, there is a chance that exhaust gas might well leak onto the side of the pneumatic actuator 5, thus having a seal ring 12 of the piston rod 6 subjected to damages by heat or the like, and thus making durability of this seal ring 12 reduced. In addition, if part of the exhaust gas is allowed to further enter into an atmospheric chamber 13 of the pneumatic actuator 5, the sliding surface of the piston 9 might well be damaged from carbon deposited thereupon, thus causing eventually a malfunction of the piston.
Among others than the above mentioned prior art construction, there are known such as disclosed in the U.S. Pat. Nos. 4,054,156 and 4,205,704 (Japanese Patent Laid-Open Application No. 54,643/1980).
In consideration of such drawbacks particular to the conventional construction of exhaust gas brake systems for use with the automotive vehicle as noted above, it would be desirable to attain an efficient resolution for overcoming such inevitable problems particular to the conventional construction.
The present invention is essentially directed to the provision of a due and proper resolution to such inconveniences and difficulties in practice as outlined above and experienced in the conventional exhaust brake systems which have been left unattended with any proper countermeasures therefor.